Magnetron



Sept. 20, i949. v A, LAlDlG 2,482,495

MAGNETRON Filed Nov. 27, 1945 I 'l;j)9.

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- ATTORNEY atented Sept. `20, 194

Alfred n. Laiaig, Bloomfield, N. Westinghouse Electric burgh,'Pa., a corporat Corporation, ion of Pennsylvania J., assig'nor to East Pitts- ApplcationvNovember 27, 1943, Serial No. 511,9ll2

(Cl. Z50-27.5)

y A11 Claims.

This invention relates to magnetrons, and contemplates an improved organization thereof as well as an improvement of specific parts `included in the assembly. y

The trend of the priorart. relating to'magnetrons has hovered around the provision of a centrally located cathode and a' surrounding anode having a plurality of resonant cavities opening inwardly towardthe' cathode. This has immediately imposed certain mechanical and electrical limitations which have confined the devices to thev conventional relationship of parts with restricted cathode area and output. One of the most serious difficulties encountered with magnetrons and which has imposed anundesirably short life, has been overheating the cathode from electron bombardment thel heat from which supplemented heat supplied by the cathode heater. l

In its general aspects, the present invention seeks to overcome the difficulties anddeciencies encountered in the conventional magnetron construction.

Likewise of general nature, an` object of the invention is to provide for materially greater cath'- ode area than possible in the conventional magnetron construction. y Y

Of closely related character is the further object of providing a construction' wherein concentration of electronic bombardment is less than in conventional magnetron construction;

A specic objectof theinventionjis to provide a cathode which girdlesor peripherally surrounds the anode. f

Another object of the invention is to uid-cool theanode, j

Yet another object of the invention is to provide a replaceableheater for the cathode and to provide such a heater which is replaceable without disturbing lthe vacuum of the magnetron.

A further object of the invention is to automatically control the heater current from the temperature of the cathode. Y' l Again, otherY objectsV of theinvention are to provide a structure which prevents relative vi'- bration between cathode and anode; to provide a structure which maybe readily and accurately machined during fabrication;V to increase the life of the magnetron as well as rated output thereof; and to provide other economies of manufacture and benefits in use. l l

Still further objects of the invention will ap'- pear to those skilled in the art as the description progresses, both by direct recitation thereof and `by inference from the. context. .YH

Referring to the accompanying drawing in which like numeralsof reference indicate similar parts throughut the several views;

Figure 1 is a, vertical section on an axial plane as indicated by lineI-I of Fig. 2 of a magnetron of my improved construction Figure 2 is a horizontal cross-section as on line lI-II of Fig.`1;' and Y Figure 3 isa diagrammatic view of the electrical circuit and automatic switching means for the heater.

In the speciiic embodiment of the invention illustrated in said drawing, the reference numeral Ill designates a generally cylindrical anode formed with a hollow hub portion II intermediate the ends of which radially project partitions I2 the side walls of which define outwardly opening "cavities I3 shown in this instance as slots. In a direction parallel to the hub axis said partitions are shorter than the hub and thereby provide an end space I4 at each end of the anode. Said cavities extend longitudinally through the anode so as to open intoV said end spaces.' Around the anode girdling the same is a cylindrical cathode I5 said cathode being spaced from the periphery of the anode and being electron emissive on its inner face toward .the anode. At the outer periphery of the cathode lare provided a pair of metallic rings I6 of equaldiameter and spaced longitudinally one from the other. Between these rings the outer face of the cathode provides a peripheral groove'II which accordingly is outwardly open enabling an arcuate heater element I8 to be sprung into the said groove'. More will be said with respect to this heater element hereinafter. 1

The aforementioned rings I6 are soldered or otherwise secured vacuumtight to the said cathode and arer coaxial therewith. They are preferably of vmaterial to which ,glass may be sealed, and may accordingly be advantageously formed from an alloy sold Vin trade under the name of Kovar the constituency of which is rdescribed in Patent2,062,335 of December 1, 1936. A ring I9 of borosilicategor other insulating material is sealed to each said metallic ring on the far edge thereof from the cathode groove, and to the far edge of Aeach glass ring is sealed another metallicY ring 20 also'preierablyV of the alloy above mentioned. 'Ihe grooved portion of the cathode, all of said metallic rings and both said glass rings constitute the peripheral wall of the magnetron. End caps 2l applied at the extreme edges' ofl metallic `rings 2D form end closures for the 'magnetronythese end caps beer extent than the entire area of the portion of the cathode at the exterior oi said enclosure. i

5. A magnetron comprising an evacuated enclosure containing a cathode and anode with the .cathode engirdling the anode and said cathode having an exterior circumferential recess therein, a substantially circular heater for and around said cathode and within said recess vand having ends spaced from each other in the recess oi said cathode, and a bim'etallic yswitch in the said recess and between the said spaced ends or" the heater,

' said switch being in series with said heater.

7. An electron discharge device comprising an y.

anode, a cylindrical cathode around said anode, said cathode having an external non-emissive face and aninternal emissive face toward said anode for discharge of electrons to the anode, a

y heater for said cathode substantially encircling said cathode intermediate the ends of the cathode at the non-emissive face thereof, and a bi-metal snap switch in series with said heater next the non-emissive face of said cathode and substantially as close to and at the same distance intermediate the ends of the cathode as the heater.

8. An electron discharge device comprising an anode, a cylindrical cathode opposed to said anode for discharge of electrons to the anode, said cylindrical cathode having a circumferential region thereof intermediate its ends constituted as a thin wall for prompt conduction of heat therethrough, the portionsof said cathode between said ends and thin-wall region providing walls of greater thickness than said thin wall for heat retention and distribution, a heater next said thin-wall region of the cathode for heating the cathode, and a heat-actuated switch -in series with said heater and in proximity to said thinwall region of the cathode for automatic control of said heater by heat condition of the cathode.

9. An electron discharge device comprising an anode, a cylindrical cathode .opposed to said anode for discharge of electrons to the anode, said cylindrical cathode having a region circumerentially thereof and intermediate the ends of the cathode constituted as a thin wall for prompt conduction of heat therethrough, the portions of said cathode between said ends and thin-wall region providing walls of greater thickness than said thin wall for heat retention and distribution, a heater circumferentially of and next said thinwall region of the cathode at the outside of and for heating said cathode, and a heat-actuated switch also at the outside oi said cathode and in series with said heater and in proximity to the thin wallY region of the cathode for automatic control of said heater by heat condition ofA said thin-wall region of the cathode.

19. An electron discharge device comprising a hollow evacuated cylindrical structure, having an outer surface exposed to theV atmosphere at the exterior thereof, an anode coaxial to and within said hollow evacuated cylindrical structure, a cylindrical cathode having an electron emitting surface within said; hollow evacuated cylindrical structure and having an outer cylindrical region constituting a part of said cuter surface exposed to the atmosphere at the exterior of said hollow evacuated cylindrical structure, and a heater for said cathode substantially encircling said outer exposed cylindrical region of the cathode exterior to the evacuated hollow cylindrical Astructure f thereby enabling said heater *tol be applied and replaced without disturbing `the evacuated condition of the said hollow evacuated cylindrical structure.

l1. An electron discharge device comprising a hollow evacuated cylindrical structure having an outer surface exposed to the atmosphere at the exterior thereof, an anode coaxial to and within said hollow evacuated cylindrical structure, a cylindrical cathode having an electron emitting surface within said hollow evacuated cylindrical Astructure and having an outer cylindrical region cathode, and an automatic heat-responsive switch in series with said heater and interposed between the ends of the same.

' ALFRED H. LAIDIG.

REFERENCES CITED Y The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,618,499 White Feb. 22, 1927 1,787,300 Alexanderson Dec. 30, 1930 1,930,084 Buttolph Oct. l0, 1933 1,957,423 Freeman May 1, 1934 2,084,867 Prinz et al June 22, 1937 2,190,668 Llewellyn Feb. 20, 1940 2,224,649` Harris Dec. 10, 1940 2,227,909 Ohl Jan. 7, 1941 FOREIGN PATENTS Number Country Date 509,102 Great Britain July 11, 1939 515,229 Great Britain Nov. 29, 1939 

